Systemic Microbiology: Parasitology
Parasitology is the branch of microbiology and pathology that deals with the study of parasites, their hosts, and the relationship between them. Parasites are organisms that live on or inside another organism (the host), deriving nutrients at the host's expense. In systemic microbiology, parasitology focuses on protozoa and helminths, which are significant causes of infectious diseases worldwide.
Protozoa and Helminths Causing Diseases
Protozoa
Protozoa are unicellular, eukaryotic organisms that often exhibit complex life cycles involving multiple stages. Many protozoan parasites cause diseases by invading tissues and multiplying within the host.Examples of Protozoa and Diseases:
Malaria (Plasmodium spp.):
- Causative Agent: Species include Plasmodium falciparum, P. vivax, P. ovale, P. malariae, and P. knowlesi.
- Transmission: Spread through the bite of infected Anopheles mosquitoes.
- Pathogenesis: The parasite infects red blood cells (RBCs), causing cyclical fever, anemia, and splenomegaly. Severe cases may lead to cerebral malaria or multi-organ failure.
- Diagnosis: Blood smears (Giemsa stain) and rapid diagnostic tests (RDTs).
- Treatment: Antimalarial drugs like artemisinin-based combination therapies (ACTs).
Amoebiasis (Entamoeba histolytica):
- Causative Agent: Entamoeba histolytica.
- Transmission: Fecal-oral route via contaminated food or water.
- Pathogenesis: Causes intestinal and extraintestinal diseases. Intestinal amoebiasis results in dysentery, while hepatic amoebiasis leads to liver abscesses.
- Diagnosis: Stool examination and serology.
- Treatment: Metronidazole or tinidazole.
- Causative Agent: Giardia lamblia (also called Giardia intestinalis).
- Transmission: Contaminated water or food.
- Pathogenesis: Parasite attaches to the intestinal mucosa, causing diarrhea, malabsorption, and abdominal cramps.
- Diagnosis: Stool microscopy or antigen detection tests.
- Treatment: Metronidazole or nitazoxanide.
Leishmaniasis (Leishmania spp.):
- Causative Agent: Leishmania donovani, L. tropica, L. major, and others.
- Transmission: Bite of infected Phlebotomus sandflies.
- Pathogenesis: Visceral leishmaniasis affects internal organs (kala-azar), while cutaneous leishmaniasis causes skin ulcers.
- Diagnosis: Bone marrow/spleen aspirates for visceral leishmaniasis; skin biopsy for cutaneous leishmaniasis.
- Treatment: Amphotericin B, miltefosine.
Trypanosomiasis (Trypanosoma spp.):
- Causative Agent: Trypanosoma brucei (African sleeping sickness) and Trypanosoma cruzi (Chagas disease).
- Transmission: Tsetse fly (African form) and triatomine bugs (American form).
- Pathogenesis: Neurological involvement in African trypanosomiasis; cardiomyopathy and mega syndromes in Chagas disease.
- Diagnosis: Microscopy, PCR, or serology.
- Treatment: Pentamidine, nifurtimox, or benznidazole depending on the disease type.
Helminths
Helminths are multicellular parasitic worms with complex lifecycles often involving intermediate and definitive hosts. They are classified into three main groups: nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes).Examples of Helminths and Diseases:
Ascariasis (Ascaris lumbricoides):
- Causative Agent: Ascaris lumbricoides.
- Transmission: Ingestion of eggs from contaminated soil or food.
- Pathogenesis: Larvae migrate through the lungs, causing respiratory symptoms, and adult worms reside in the intestines, leading to obstruction or malnutrition.
- Diagnosis: Stool examination for eggs.
- Treatment: Albendazole or mebendazole.
Hookworm Disease (Ancylostoma duodenale and Necator americanus):
- Causative Agents: Ancylostoma duodenale and Necator americanus.
- Transmission: Larvae penetrate the skin, often from walking barefoot on contaminated soil.
- Pathogenesis: Larvae migrate to the lungs and intestines, causing anemia and protein loss.
- Diagnosis: Stool examination for eggs.
- Treatment: Albendazole or mebendazole.
Schistosomiasis (Schistosoma spp.):
- Causative Agents: Schistosoma mansoni, S. haematobium, S. japonicum.
- Transmission: Skin contact with contaminated freshwater containing infective larvae (cercariae).
- Pathogenesis: Chronic infection causes bladder or intestinal damage and fibrosis. S. haematobium can lead to bladder cancer.
- Diagnosis: Urine or stool examination; serology.
- Treatment: Praziquantel.
Taeniasis and Cysticercosis (Taenia solium and Taenia saginata):
- Causative Agents: Taenia solium (pork tapeworm) and Taenia saginata (beef tapeworm).
- Transmission: Ingestion of undercooked infected meat (taeniasis) or eggs (cysticercosis).
- Pathogenesis: Intestinal infection (taeniasis) or larval encystment in tissues, including the brain (neurocysticercosis).
- Diagnosis: Stool examination for taeniasis; imaging for cysticercosis.
- Treatment: Praziquantel or albendazole.
Lymphatic Filariasis (Wuchereria bancrofti, Brugia spp.):
- Causative Agents: Wuchereria bancrofti, Brugia malayi, Brugia timori.
- Transmission: Spread by mosquito vectors.
- Pathogenesis: Parasites reside in lymphatic vessels, causing lymphedema and elephantiasis.
- Diagnosis: Blood smear, antigen tests.
- Treatment: Diethylcarbamazine (DEC) or ivermectin with albendazole.
General Diagnosis and Management of Parasitic Diseases
- Microscopy (stool, blood, or tissue samples).
- Serology (antigen/antibody detection).
- Molecular methods (PCR).
- Imaging techniques (for cysticercosis or visceral leishmaniasis).
- Sanitation and hygiene (handwashing, safe drinking water).
- Vector control (use of insecticides, bed nets).
- Vaccination (under development for some diseases).
- Anti-parasitic drugs (e.g., albendazole, praziquantel, metronidazole).
- Symptomatic management (antipyretics, hydration).
- Nutritional support for affected individuals.
Comments
Post a Comment